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Re: st: variable not found?


From   Yuval Arbel <yuval.arbel@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: variable not found?
Date   Mon, 24 Oct 2011 11:54:06 +0200

Paul,

It seems the purpose of this exercise is to show you that running a
regression on a dummy variable GROUP is an elegant way to find whether
the difference of means between the groups is significant or not.

I ran below the mvreg based on the data you gave. Note, for example,
that while the motivation for GROUP=1 decreases by 7.428 points, this
coeffiecient is insignificant (t-value of -0.62). It implies that
statisticallty there are no motivation differences between the two
groups. On the other hand, the motivation for GROUP=1 is lower by
7.428 points

In other words, the test

. mvreg motiv aspire algebra geom = group

Equation          Obs  Parms        RMSE    "R-sq"          F        P
----------------------------------------------------------------------
motiv               8      2    16.44815    0.0599   .3823938   0.5591
aspire              8      2    12.11901    0.0090   .0543859   0.8234
algebra             8      2    13.90122    0.1842   1.354984   0.2886
geom                8      2    11.11769    0.1715   1.241692   0.3078

------------------------------------------------------------------------------
             |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
motiv        |
       group |  -7.428001   12.01203    -0.62   0.559    -36.82039    21.96439
       _cons |      55.73   9.496346     5.87   0.001     32.49328    78.96672
-------------+----------------------------------------------------------------
aspire       |
       group |  -2.063999   8.850472    -0.23   0.823    -23.72032    19.59233
       _cons |      73.02   6.996913    10.44   0.000     55.89917    90.14083
-------------+----------------------------------------------------------------
algebra      |
       group |  -11.81733   10.15202    -1.16   0.289    -36.65842    13.02376
       _cons |   62.40333   8.025874     7.78   0.000     42.76473    82.04194
-------------+----------------------------------------------------------------
geom         |
       group |  -9.047335    8.11921    -1.11   0.308    -28.91433    10.81966
       _cons |   78.57333   6.418799    12.24   0.000      62.8671    94.27957
------------------------------------------------------------------------------



On Mon, Oct 24, 2011 at 3:53 AM, Paul Burkander <paul@burkander.com> wrote:
> Hi all,
>
> I'm trying to help my wife do some stata homework, and we've run into
> some odd behavior.
>
> Below is a sample of the data.  She's supposed to do a manova of
> MOTIV,ASPIRE,ALGEBRA,GEOM, on GROUP , then mvreg, then test the
> restriction that the coefficients on GROUP are zero in all four
> equations.  After doing the manova and mvreg, we typed test GROUP, but
> receive the error message "GROUP not found."
>
> Any ideas?  Perhaps we're doing something dumb?  She entered the data
> by pasting into the data editor.  We're using Stata 11 SE and I just
> did a full update.
>
> Thanks, Paul
>
> MOTIV,ASPIRE,ALGEBRA,GEOM,GROUP
> 74.31,78.57,68.59,78.57,1
> 27.15,61.91,37.15,71.43,1
> 64.31,90.48,67.16,83.34,1
> 40.01,64.29,48.59,59.53,1
> 35.73,59.53,31.44,54.76,1
> 55.73,83.34,60.02,85.72,0
> 52.87,64.29,62.88,69.05,0
> 58.59,71.43,64.31,80.95,0
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>



-- 
Dr. Yuval Arbel
School of Business
Carmel Academic Center
4 Shaar Palmer Street, Haifa, Israel
e-mail: yuval.arbel@gmail.com

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


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